Biochemical analysis of Angelman syndrome-associated mutations in the E3 ubiquitin ligase E6-associated protein
Biochemical analysis of Angelman syndrome-associated mutations in the E3 ubiquitin ligase E6-associated protein
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DOI：
10.1074/jbc.m401302200
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发表时间：
2004-09-24
影响因子：
4.8
通讯作者：
Howley, PM
中科院分区：
文献类型：
--
作者：
Cooper, EM;Hudson, AW;Howley, PM
Angelman综合征是一种严重的神经系统疾病，其特征是精神发育迟滞、言语缺失、共济失调、癫痫发作和多动。这种疾病中受影响的基因是UBE3A，编码E6相关蛋白（E6AP）泛素蛋白连接酶的基因。大多数患者具有染色体缺失，其去除了UBE3A的整个母体等位基因。然而，一小部分患者具有E6AP点突变，导致单个氨基酸变化或短的框内缺失，仍然允许全长蛋白质的翻译。通过研究E6AP中的这些点突变，我们发现Angelman相关突变与E3泛素连接酶活性丧失之间存在很强的相关性。有趣的是，点突变以不同的方式影响E6AP活性。一些突变蛋白不能与泛素形成硫羟酸酯中间体，另一些保留硫羟酸酯形成活性但不能有效地将泛素转移到底物，还有一些在细胞中不稳定。我们的研究结果表明，E6AP催化活性的丧失和可能的E6AP底物的不适当调节在Angelman综合征的发展中是重要的。
Angelman syndrome is a severe neurological disorder characterized by mental retardation, absent speech, ataxia, seizures, and hyperactivity. The gene affected in this disorder is UBE3A, the gene encoding the E6-associated protein (E6AP) ubiquitin-protein ligase. Most patients have chromosomal deletions that remove the entire maternal allele of UBE3A. However, a small subset of patients have E6AP point mutations that result in single amino acid changes or short in-frame deletions that still allow translation of a full-length protein. By studying these point mutations in E6AP, we found a strong correlation between Angelman-associated mutations and a loss of E3 ubiquitin ligase activity. Interestingly the point mutations affect E6AP activity in different ways. Some mutant proteins cannot form thiol ester intermediates with ubiquitin, others retain the thiol ester formation activity but cannot efficiently transfer ubiquitin to a substrate, and still others are unstable in cells. Our results suggest that the loss of E6AP catalytic activity and likely the improper regulation of E6AP substrate(s) are important in the development of Angelman syndrome.